Today, turbopumps are used in a wide variety of applications. One example of such an application is rocket propulsion systems. Many rocket propulsion systems include turbopumps as part of a propellant feed system. Turbopumps may be used, for example, to convey various fluids (e.g., fuels and oxidizers) to a combustor of the rocket engine. Turbopumps consist of turbine and pump components. The pump typically increases these incoming fluids to a higher pressure.
The rotational seal is typically formed between a rotating portion of the pump (e.g., centrifugal pump impeller) and a stationary portion of the pump. High rotational speeds can cause the rotating member forming this seal to bow outwardly or scallop. One approach for restricting the amount of scalloping is to increase the thickness of the rotating member of the seal. Another approach, is to provide a larger seal clearance to accommodate the scalloping. However, the larger seal clearances tend to reduce the efficiency of the pump. In other words, pump impeller efficiency usually decreases with increases in seal clearances.